The invention relates to a method of analyzing a crystal structure of a specimen based on the strength of the X-rays that are diffracted from the specimen after the irradiation of the X-rays on the specimen having a crystal structure.
A X-ray diffraction method using xcex8-2xcex8 scan with X-ray is well known as a method for analyzing crystal phases of crystalline thin films.
Crystalline thin films may often contain different crystal phases dependent on the film-forming conditions. For example, when a thin film of SrBi2Ta2O9 (hereinafter referred to as SBT) is formed on a Pt/TiO2/(001)Si substrate, it is well known that this SBT thin film has in most cases a crystal phase called SBT phase, but in some cases it also has a so-called fluorite phase, which is a different crystal phase from the SBT phase, dependent on the film-forming conditions. It is quite difficult for the conventional X-ray diffraction method to distinguish between the SBT phase and the fluorite phase because the diffraction angles (2xcex8) of SBT phase and fluorite phase are similar. Thus, there exists a problem of difficulty in analyzing crystal structures in detail using the conventional X-ray diffraction method if the diffraction rays from different crystal phases appear within an approximately same angle.
In view of the above-mentioned background, it is an objective of the invention to provide a crystal structure analysis method for analyzing crystal structures in detail.
A crystal structure analysis method provided by the invention in order to achieve the above-described objective comprises the steps of irradiating X-rays onto a specimen having a crystal structure, detecting the said X-rays that are diffracted from the said specimen and analyzing the said crystal structure of the said specimen based on the strength of the said detected X-rays, wherein the said step of analyzing the said crystal structure of the said specimen is performed based on the strength of first X-rays diffracted from first crystallographic planes that align so as to keep a first crystallographic plane distance between each other and the strength of second X-rays diffracted from second crystallographic planes that extend diagonally relative to the said first crystallographic planes and align so as to keep a second crystallographic plane distance between each other.
According to the invention, in order to analyze the crystal structure of the specimen, not only the strength of the first X-rays diffracted from the first crystallographic planes that align keeping said first crystallographic planes at a distance from each other but also the strength of the second X-rays diffracted from the second crystallographic planes that extend diagonally relative to the said first crystallographic planes and align keeping a second crystallographic plane distance each other are detected. In such way to detect the strength of the X-rays diffracted from the first and second crystallographic planes that extend diagonally each other, the crystal structure can be analyzed more in detail in the inventive method than in the conventional method.
Besides, the inventive method preferably includes irradiating X-rays onto the specimen with variable incident angles relative to the said specimen within each of a plurality of planes that respectively intersect with the said specimen with respective different angles relative to the said specimen, so that it may be easy to detect the X-rays diffracted from the first and second crystallographic planes that extend diagonally from each other.
Moreover, the inventive method preferably includes incrementing (or decrementing) the variable incident angles relative to the said specimen within an angle range between the incident angle when the said first X-rays have come into the said specimen and the incident angle when the said second X-rays have come into the said specimen. By changing the incident X-rays within such range, it is possible to detect the X-rays diffracted from other crystallographic planes than the said first and second crystallographic planes.
Furthermore, the said plurality of planes intersect each other and have respective tilting angles in a range of 0 to 90 degrees relative to the said specimen, and the inventive method preferably includes incrementing (or decrementing) the said variable incident angles within a range of angles of 0 to 90 degrees. In this way, the crystal structure can be analyzed more in detail.
The inventive method may comprise tilting the said specimen with variable tilting angles relative to one plane that intersects with the said specimen, irradiating the X-rays having variable incident angles within the said one plane onto the respective specimen tilted with one of the said variable tilting angles and detecting the said X-rays that are diffracted with the said specimen. In the embodiment, one plane that intersects with the specimen is considered. By also changing the tilting angle and the incident angle relative to the said one plane, it is possible to detect the strength of the X-rays diffracted from the first and second crystallographic planes that extend diagonally from each other. Therefore, the crystal structure can be analyzed more in detail in comparison with the conventional method.
Furthermore, in the inventive method, the said specimen is preferably a bismuth layer structured compound. The bismuth (Bi) layer compound may contain various crystal phases such as a SBT phase, a fluorite phase and a pyrochlore phase. If there is a possibility that a specimen may contain such multiple crystal phases, the conventional methods have difficulties in discriminating the crystal phase of the specimen. The inventive method can distinguish the crystal structure of the specimen very precisely even if the specimen (e.g., Bi-layer compound) contains various crystal phases.